Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. When an airplane banks its wings for a turn, the increased lift of the raised wing results in increased drag, which causes the airplane to yaw or swing toward the side or direction of the raised wing. Adverse yaw can be countered by using the rudder, which creates a side force on the vertical tail that opposes adverse yaw. There are two types of ailerons that can be used to reduce adverse yaw: differential ailerons and frise ailerons. Student pilots train to overcome adverse yaw in a number of ways, including using the rudder as the airplane banks into the turn.